A peripheral for use with the Kookaberry
This sensor is an INPUT device. It measures the moisture in a ground medium such as soil. It is an analogue device.
It measures soil moisture levels by capacitive sensing, rather than resistive sensing like other types of moisture sensor. It is made of a corrosion resistant material giving it a long service life. Insert it into soil and measure real-time soil moisture data!
SPECIFICATION
- Operating Voltage: 3.3 ~ 5.5 VDC
- Output Voltage: 1.2 ~ 2.5V
- Interface: PH2.0-3P
- Dimension: 98mm * 23mm (3.86in x 0.905in)
- Weight: 15g
How does it Work?
The sensor is plugged into the Kookaberry technology platform in accordance with the app instructions
When inserted into soil, it uses the change in capacitance of the probe to measure variation in the moisture content of soil. It does not measure the moisture content of the soil directly as it measures the ions that are dissolved in the moisture. The amount of ions dissolved in the moisture will depend upon the soil type, chemistry, amount of fertiliser in the soil etc. These ions effect the capacitance of the probe by varying the dielectric properties of the sensor.
On board the sensor is an oscillator with the frequency of this oscillator being controlled by the capacitance of the sensor. When the sensor is inserted into the soil and as the soil becomes wetter, the capacitance of the sensor changes which in turn varies the frequency of the sensor’s internal oscillator. This oscillator frequency is then changed into an analogue value which can be measured at Pin 3 on the JST PH connector on the sensor.
Due to manufacturing processes each sensor may vary slightly in its initial value of capacitance and thus the oscillator frequency may vary giving slightly variable output voltages for wet and dry conditions.
The sensor can be calibrated to show DRY at 0% and WET at 100% using the script below. First run the script with the sensor in dry air and then put it into a glass of water – BUT NOT HIGHER THAN THE WHITE LINE. The electronics are not waterproof.
Leave it for a minute to stabilise after putting it into the water.
Measure the voltages at DRY and WET and insert them into the scripts used in the Soil Moisture Sensor (Capacitive) app.
KookaBlocs Calibration Script
Python Calibration Script
Where is this used in real life?
This is a relatively low tech sensor, but ideal for monitoring an urban garden or your pet plant’s water level.
Sensors such as this provide the feedback data to automatically water plants in aquaculture projects
How can they be used to enhance Lesson Plans outcomes?
- Sustainable food production and agriculture
- Sustainable micro-climate (Terrarium)
